A plasma display panel of the prior art comprises, as shown in FIGS. 1A and 1B, a first plate 1, generally provided with at least a first and a second array of coplanar electrodes Y, Y′, and a second plate 2 provided with an array of electrodes X, called address electrodes. The address electrodes form a two-dimensional set of elementary discharge regions, filled with a discharge gas, each positioned at the intersection of an address electrode X and a pair of electrodes of the first and the second array of coplanar electrodes.
In this type of display panel, it is possible to generate, in each elementary discharge region either what are called matrix discharges, when these take place between the address electrode and one of the two coplanar electrodes serving this region, or what are called coplanar discharges when these take place between the two coplanar electrodes serving this region.
The methods for driving a panel of this kind are suitable for displaying images divided into a succession of frames, in which each frame is itself divided into a succession of subframes in order to generate the various grey levels, where each subframe generally comprises an address phase followed by a sustain phase. During each address phase, a matrix discharge is generated in those discharge regions of the panel that have to be activated during the subframe, that is to say during the sustain phase that follows. During each sustain phase, a succession of voltage pulses is generated between the coplanar electrodes so as to cause display discharges only in those discharge regions that have been activated beforehand.
Thus, the matrix discharges are generally caused only during address phases, or phases other than the sustain phases, such as for example the reset phases. Documents EP 1 294 006 and U.S. Pat. No. 6,295,040 illustrate such image display devices, and also the article entitled “A new method to reduce addressing time in a large AC plasma display panel” in IEEE Transactions on Electron Devices, Vol. 48, No. 6, June 2001, pp. 1082-1096, which describes a plasma display panel structure enabling the duration of the address phases for each subframe to be shortened.
The electrodes of both the first and second array of coplanar electrodes of the plate 1 are generally directed so as to be mutually parallel. Each electrode Y of the first array is adjacent to an electrode Y′ of the second array, is paired with it and is intended to serve a set of coplanar discharge regions, and vice versa for each electrode Y′ of the second array.
The arrays of coplanar electrodes are coated with a dielectric layer 3 in order to provide a memory effect. The dielectric layer 3 itself being coated with a protective and secondary-electron-emitting layer 4, generally based on magnesia.
The adjacent elementary discharge regions, at least those that emit different colors, are generally bounded by horizontal barrier ribs 5 and/or vertical barrier ribs 6. These barrier ribs generally serve also as spacers between the plates.
The address electrodes are generally covered with a layer of dielectric material 7 in order to provide a memory effect. The dielectric material 7 layer has a uniform thickness in that part of the plate 2 which forms the wall of the discharge region.
As shown in FIG. 1A, within each elementary discharge region, the area of the discharge region located plumb with each of the coplanar electrodes lying between x=0 and x=Le, can be subdivided into several regions along the direction of the OX axis perpendicular to the general direction of the coplanar electrodes. First, a conducting region Za, called the coplanar discharge ignition region, lying between X=0 and X=La, one of the boundaries of which forms an ignition edge, or internal edge, facing the other coplanar electrode of the same elementary discharge region. Second, a conducting region Ze, called a coplanar discharge expansion region, lying between X=La and X=Le, located at the rear of the conducting ignition region opposite the other coplanar electrode; one of the boundaries of this expansion zone forms an end-of-expansion edge or external edge, opposite the ignition edge. Third, a conducting region Zm, called a coplanar matrix discharge region, lying between X=Xm1 and X=Xm2, encroaching both on the coplanar discharge ignition region and on the coplanar discharge expansion region defined above, which includes at least one part of the region where the coplanar electrode in question crosses the address electrode in the discharge region.
In each discharge region or cell of the display panel, the address electrode therefore crosses two coplanar electrodes. In each of the two corresponding crossing regions, we may define on the coplanar electrode, a coplanar matrix discharge conducting region Zm and on the address electrode, a matrix discharge conducting region Zmx.
The “gas height” in each cell of the display panel corresponds to the gap separating the two plates. The gas height is approximately constant in each cell, and therefore identical in the case of the two matrix discharge regions of each cell. The gas height in the matrix discharge region corresponds to the gap between the regions Zm and Zmx in this region.
An elementary discharge region or cell of the display panel therefore comprises at least two matrix discharge regions extending between the plates and a coplanar discharge region extending over the first plate at the coplanar electrodes and between them. Each set of elementary discharge regions served by one and the same pair of electrodes corresponds in general to a horizontal row of elementary discharge regions, cells or subpixels of the display panel. Each set of elementary discharge regions served by one and the same address electrode corresponds in general to a vertical column of elementary discharge regions, cells or subpixels.
The walls of the discharge regions are generally partly coated with phosphors sensitive to the ultraviolet radiation from the luminous discharges. Adjacent column discharge regions are provided with phosphors that emit different primary colors, so that the combination of these three adjacent elementary regions or subpixels in one and the same row forms a picture element or pixel.
The cell shown in FIGS. 1A and 1B is of rectangular shape (other cell geometries have been disclosed in the prior art). The largest dimension of this cell lies parallel to the address electrodes X, where Ox is the longitudinal axis of symmetry of this cell. In each elementary discharge region served by a pair of electrodes and forming a discharge cell, the portions of electrodes Y, Y′ bounded by the vertical barrier ribs 6 separating the columns have a width LE measured parallel to the Ox axis. This electrode width LE is in this case constant over the entire width of the cell.
To display an image of a video sequence, a conventional exclusively coplanar-sustain drive method is used. By means of the array of address electrodes and of one of the arrays of coplanar electrodes, each row of the display is addressed in succession by depositing electrical charges in the dielectric layer region of each discharge region of this row that has been preselected, the corresponding subpixel of which has to be activated in order to display the image. Then, by applying series of sustain voltage pulses between the coplanar electrodes serving the regions that have just been addressed, series of sustain pulses are produced only in the regions charged beforehand, thereby activating the corresponding subpixels and allowing the image to be displayed.